Reaction products of formaldehyde and sodium cyanamide



Patented Nov. 19, 1946 2,4113% REACTION rnonuc'rs F Foamtnnnm AND SODIUMCYANAMIDE Joseph Frederic Walker, Lewiston, N. Y., assignorto E. I. duPont deNemours & Company, Wilmington, Del., a corporation of DelawareSerial No. 507,182

No Drawing. Application October 21, 1943,

9 Claims.

This invention relates to certain new and valuable products secured byreacting formaldehyde with sodium cynanamide. More particularly, it isconcerned with the preparation of formaldehyde-sodium cyanamidecondensation products by reacting the two chemical compounds in anaqueous solution, the temperature being maintained at room temperatureor below, and the reaction being carried out under alkaline conditions.I 10 aqueous acids or strong alkalis and is practically .It is thereforeone of the objects of this inveninsoluble in Wat r. the pr t ein lea tolution to prepare novel condensation products by ble in aqueous liquidshaving a pH of 8.0-9.0. reacting formaldehyde and sodium cyanamide. Whendissolved in aqueous alkalies or acids it Another object of thisinvention is to prepare may be precipitatedtherefrom, although the theseproducts, valuable as electroplating addil5 yields upon reprecipitationare not entirely quantion agents and for other purposes, by carryingtitative.' Analyses of the reprecipitated product out the reaction in areaction medium which is indicate that its composition is substantiallyunsubstantially alkaline in reaction. These and chan edstill furtherobjects of my invention will be ap- In carrying out the reaction solidsodium cyparent from the ensuing disclosure of certain anamide ispreferably added to an aqueous solupreferred embodiments thereof. tionof formaldehyde at a temperature some- I have now found that acondensation product what below room temperature. The temperaof sodiumcyanamide and formaldehyde can he ture will tend to increase during thereaction, and obtained in fair yields by the addition of sodium coolingwill be necessary. The temperature of cyanamide to fairly cold aqueousformaldehyde the reaction mixture should be maintained gensolutions, andthat it may be isolated as a watererally within the range of 15-20 0.althou h insoluble precipitate by neutralization of excess p t f as e eate as' C. if ma ntained for alkalinity in this solution. The reactioniscaronly rt periods of time are not objectionable. ried out underalkaline conditions at a tempera- I have found a temperature as high as25 C. ture below 35 C., preferably. in th range 15 to maintained forsome length of time not objec-, 20 C. At the end of the reaction periodthe tionable. When the acid added to pre product may be precipitated bythe addition of the reaction product is added in successiveporsuificient acid to reduce the high alkaline pH of tions, or n t sadded in S a increments the mixture to a'value in the pH range 3 m9,over the entire reaction period, or over substan- The product i probablya partially hydrated tially the entire reaction period, it is notnecespolymer of methylene cyanamide (CH2=NCN) in a y to e ri h pp r te pr re limit so which approximately two-thirds of the CN radicarefullyduring-the la ter stages of the process, cals have been converted toamide groups. and' somewhat more elevated te per tu es can Analyses forcarbon, hydrogen, and nitrogen inbe maintained without interference withthe redicate that its composition closely approximates to action-Ordinary commercial aq solutions the empirical formula, CsHroNcOz. Thecharacof formaldehyd 0nt n f C 2 m y be teristics of the product arethose of an amorphous u l d e y, y y be diluted t $0111- resin, and itis probably not a simple compound of tions of approximately 20% CHzOconcentration low molecular weight but rather a polymer or or lessbefore being utilizedinthe reaction. mixture of polymers made up ofunits. eorre- When the reaction is carried out at approxisponding to theCsHzoNeOz formula. It is bemately room temperature it is substantially 0lieved that the structural formula of this polymer plete at the end ofabout four to six hours. A unit is as follows: mineral acid such ashydrochloric aciicll, sulfuric acid, phosphoric acid, or any other fa lystrong CONE ON CONE acid, for example acetic acid, may then be added*CHPN CH= N CHQ N in amount suflicient to adjust the pH of the re- Thenew condensation product is a white, apaction mixture to oneapproximately within the parently-non-crystalline solid which chars whenv range of 8.0-9.0. This causes the formaldehydeheated to temperaturesabove 300 C. Although sodium cyanamide condensation product toprecipitate. If desired, the hydrochloric acid or it is apparentlystable when heated below 300 C.

when dry, it undergoes further resiniflcation when heated in the moiststate and should be dried quickly and at relatively low temperatures toavoid undesirable alteration. On long heatin in the moist state itcombines with additional water and tends to liberate ammonia. A sampleheated-in this way was found to have an empirical compositioncorresponding to CcHiaNsOa.

The new product dissolves readily in dilute 2,dll,896

other mineral acid may be added in successive small portions at variousstages of the reaction following the addition of the sodium cyanamide tothe formaldehyde, or it may be added more or less continuously in smallincremental amounts during the entire reaction period. Under theseconditions the reaction of sodium cyanamide and formaldehyde takes placeconcomitantly with the neutralization of the alkali. As previouslystated, the addition of the mineral acid portionwise, or continuouslyduring the reaction, also has the advantage of permitting themaintenance of temperatures somewhat above 25 C. during the latterstages of the process without interference with the reaction, thussimplifying the problem of cooling the reaction mixture.

The solution containing the precipitated condensation' product may nowbe allowed to stand for two or more hours, or overnight, to insurecomplete precipitation. The filtered product may then be washed withwater, dried, ground, and

packed. I have secured very satisfactory drying with only slightdiscoloration, and with no caking, sintering or charring of thecondensation product, by the use of a current of warm air at atemperature of 80 to90 .F. However, drum drying on a heated rotatingdrum has also given very satisfactory results. Thedried product usuallytends to have a reddish or brownish cast un e s vacuum dried at roomtemperature.

The new condensation product is valuable as an addition a ent inelectroplating baths, and is also believed suitable for use as aflame-proofing agent. in the manufacture of heat-resistant resins, andin the case-hardening of ferrousmetals.

As an example of my process for preparing the formaldehyde-sodiumcyanamide condensation product, the following may be. given:

Sodium cyanamide (technical grade approximate y 94%) in the amount of17.9 lbs. was reacted with 16.1 lbs. of commercial 3'7 formaldehydesolution. The solid sodium cyanamide was added to the formaldehydesolution, which was contained in a 15-gallon stoneware crock equippedwith a stainless steel cooling coil and a stainless steel propelleragitator. Before the addition of the solid sodium cyanamide in granularform the formaldehyde was cooled to about 5 C. by the addition of ice tothe solution. The granular sodium cyanamide was added gradually,

in successive small increments, ice being added during the addition tokeep the temperature be- 1ow-about 20 C. Following this, 23%hydrochloric acid was added continuously at a rate of about 12 lbs. perhour until the pH of the reaction mixture had fallen to a value in therange pH 8-9. Approximately 62.9 lbs. of 23% acid were required for thispurpose. The temperature of the reaction mixture was maintained in therange 15 to 20 C. throughout this period, precipitation of productoccurring during addition of the last half of the acid.

The precipitate was in a finely-divided form and was white or colorless.The reaction mixture was allowed to stand overnight before filtration inorder to insure complete precipitation of the product. The condensationproduct was then filtered off, washed thoroughly with water and driedwith hot air at a temperature of 80-100 F. This temperature was employedin the drying since at higher drying temperatures there is danger thatthe product may cake to form a brittle, dark red or reddish brown resin.Drum drying using a heated rotating drum on which the product remainsfor only a. short period This reaction evidently takes place in twostages: (-1) condensation of sodium cyanamide. and formaldehyde and. (2)neutralization of alkali with resultant precipitation of finishedproduct. Each stage of the reaction is exothermic.

Other suitable modifications and changes as will be obvious to a skilledchemist may be made in carrying out my process, without departing fromthe spirit or scope thereof. The scope of my invention is accordinglyintended to include these variations and modifications, to the extentthat they are comprehended within the scope ofthe appended claims.

I claim: I

l. The process of preparing condensation products of sodium cyanamideand formaldehyde which comprises reacting, as the sole reactants, saidcompounds in substantially equimolar proportions in an aqueous alkalinereaction medium having a pH above 9 and approximately the pH .of saidaqueous solution of equimolecular proportions of sodium cyanamide andformaldehyde, the temperature during said reaction being maintainedbelow about 25 C.

2. The process of preparing condensation products of sodium cyanamideand formaldehyde which comprises reacting, as the sole reactants, saidcompounds in substantially equimolar proportions, at a temperature notexceeding 35 C. in an aqueous alkaline reaction medium having a pH above9 and approximately the pH of said aqueous solution of equimolecularproportions of sodium cyanamide and formaldehyde, and adding to saidreaction a mineral acid in sufficient amount to adjust the pH of saidreaction mixture to one within the range 3.0-9.0, thereby precipitatingsaid condensation product.

3. The process of preparing condensation products of sodium cyanamideand formaldehyde which comprises reacting, as the sole reactants, saidcompounds in substantially equimolar proportions in an aqueous alkalinereaction medium having a pH above 9 and approximately the pH of saidaqueous solution of equimolecular proportions of sodium cyanamide andformaldehyde, cooling said reaction medium during said reaction so thatthe temperature does not exceed, 25 C., and adding a mineral acid insuflicient amount to insure a pH of said reaction medium within therange 8.0-9.0 at the conclusion of the reaction, whereby saidcondensation product is 2,411,sae

pH above 9 and approximately the pH of said ueous solution ofequimoleciilar proportions sodium cyanamide and formaldehyde, and dinghydrochloric acid thereto in amounts suf- :ien't to insure a pH of saidreaction medium thin the range 8.0-9.0 at the conclusion of the action,whereby said condensation product is ecipitated in said aqueous reactionmedium. 5. The process of preparing condensation prod- :ts of sodiumcyanamide and formaldehyde aich comprises reacting, as the solereactants, id compounds in substantially equimolar prortions in anaqueous alkaline reaction medium wing a pH above 9 and approximately thepH said aqueous solution of e uimolecular proporms of sodium cyanamideand formaldehyde, cling said reaction medium during the reaction thatthe temperaturedoes not exceed about C., and adding hydrochloric acidthereto in nounts sumcient to insure a pH within the nge of 8.0-9.0 atthe con'clusion of the reaction, hereby the desired condensation productis prepitated in said reaction medium. 6. The process which comprisesadding, in subantially equimolar proportion, solid sodium 'anamide to anaqueous solution of formaldevde to form a reaction mixture in which saidvo substances are the sole reactants, maintainig the resulting reactionmixture at a temperalre below about 25 C. and at a pH above 9 1dapproximately the pH of said aqueous soluon of equimolecular proportionsof sodium cynamide and formaldehyde, adding thereto a mineral acid inamount sufllcient to adjust the pH of the reaction mixture to one withinthe range 8.0-9.0, and recovering the precipitated condensation productfrom said reaction mixture.

7. The process which comprises adding, in substantially equirnolarproportions, solid sodium cyanamide to an aqueous solution offormaldehyde to form a reaction mixture in which said two substances arethe sole reactants, maintaining the temperature of the resultingreaction mixture below about 25 C. and at a pH above 9 and approximatelythe pH of said aqueous solution of equimolecular proportions of sodiumcyanamide and formaldehyde, adding hydrochloric acid thereto in amountsufiicient to adjust the pH of said reaction mixture to one within therange of 8.0-9.0, and recovering the'precipitated sodiumcyanamide-formaldehyde condensation product from said reaction mixture.

8. The condensation product of sodium cyanamide and formaldehydeobtained by the process of claim 1 having the empirical formulaCsHroNeOz, said product being a white, apparently I

